Terpolymers of chitosan with acrylamide and sodium salt of acrylic acid as prospects flocculants and sorbents

Abstract

Amphoteric polymers based on chitosan, acrylamide and sodium acrylate with different content of the latter were synthesized using the radical copolymerization method in solution in the presence of 1.4 × 10^–3 mol/L ammonium persulfate in an inert medium at 333 K. Terpolymers’ molecular weight characteristics, their structure, as well as the ability to flocculation and sorption of hydrogels based on them were investigated. The copolymers’ formation was proved by extraction, IR-spectroscopy, conductometric titration, differential scanning calorimetry, and statistical light scattering. The chitosan modification with acrylamide leads to an increasing of its molecular weight up to 5.2 × 10⁵. The subsequent introduction of the sodium acrylate into the copolymer allows obtaining terpolymers with molecular weight from 7.7 × 10⁵ to 18.5 × 10⁵ depending on the amount of the introduced monomer. The maximum content of acid groups in the graft copolymers reached 26.8 wt%. Copolymers exhibit pH sensitivity. Copolymers can be used as effective flocculants which was shown on the model system of 1 wt% kaolin solution in water. Hydrogels based on graft copolymers of chitosan with acrylamide and sodium acrylate were prepared by the of radical polymerization method in solution. Their water absorption capacity at different pH was investigated under several swelling-drying cycles. It was shown that hydrogels can be used as effective sorbents of Mn²⁺ and Fe²⁺ ions from model solutions.

at 296 K.